There is a growing list of players who were designated for assignment by their previous MLB teams, only to very quickly experience newfound success with the Miami Marlins. That list includes Declan Cronin, who was Miami’s most effective reliever for an extended stretch of the 2024 season. Cronin showed a lot of versatility as a rookie—he frequently went multiple innings, worked back-to-back days and inherited baserunners depending on what the club needed from him. He pitched a total of 70 ⅓ innings with a pedestrian 4.35 ERA, but a far more encouraging 2.58 FIP.
However, Cronin was unable to build upon that campaign in 2025 because of a series of injuries. Anything he achieves once he fully recovers will transpire in a different uniform.
Cronin’s age-27 season got off to a delayed start. During spring training, he suffered what was publicly announced as a left hip strain. Cronin got much more specific in an interview with Ben Lindbergh on Friday’s episode of Effectively Wild, explaining that incorporating a new drill into his workout routine caused damage to “delicate little muscles” in his hip. Rotating his hips while going through his pitching delivery aggravated the injury.
“What I probably should’ve done was taken some serious time off from throwing, just actually allowing the muscles and the tissue to fully heal before putting them through that stress again,” Cronin said. “But I wanted to kind of ‘go, go, go,’ so we ‘kept the arm moving,’ kept throwing.” He began a rehab assignment with Triple-A Jacksonville on April 10. While making back-to-back appearances on April 12-13, he had a setback and was “back to square one.”
A hip specialist in Nashville provided Cronin with a different interpretation of his unique injury and his rehab plan changed accordingly. A month later, he was throwing pain-free and cleared to face live batters again. Although Cronin’s velocity and pitch shapes weren’t all the way back to his 2024 form, “I and everyone else kinda thought, ‘Okay, you’re just getting back into the swing of it. You gotta remember this is kinda like a second offseason/on-ramp for you.'” When the Marlins optioned Cronin to Jacksonville on May 31, he believed that he was only a week or two away from being major league-ready.
Unfortunately, “I just never got back to what I felt like before the hip injury,” Cronin said. “My body had patterned—over months of low-intensity throwing and/or throwing with pain—certain kind of compensatory movement patterns that just totally compromised by ability to throw how I want to throw. Even though I was pain-free, I could not convince myself to throw normally and to use my lower half specifically normally.” That led indirectly to shoulder pain. Even when that subsided and Cronin returned from another IL stint in early August, he still felt out of sync. “Something has to give here,” he remembered thinking at the time.
Indeed, on August 16, his right UCL gave out. “I immediately knew,” Cronin said. “I could feel the space in my elbow expand at ball release…I kinda felt that ‘pop’ and release of tension.”
From his last appearance on August 16…Cronin knew right away that something was very wrong.
Now officially sidelined for the whole 2026 season. https://t.co/z0jgGhRUqW pic.twitter.com/WlCHp8hNxZ
— Fish On First (@FishOnFirst) September 30, 2025
After consultation with renowned surgeon Dr. Keith Meister, it was clear that Cronin would need Tommy John surgery. Cronin was under the impression that the Marlins would be retaining him for the 2026 season, placing him on the 60-day IL throughout the year-long rehab process. That’s what they will be doing for Ronny Henriquez, who had his own elbow surgery earlier this month.
Instead, before the procedure even took place, the Marlins released Cronin on September 6. “It was very surprising,” he said. “Certainly not something that I anticipated or anybody close to me anticipated. It also kinda wasn’t what we had been told and nothing I’d ever seen before, but check the rulebook, they’re allowed to do it, so power to them to exercise their rights.”
The Marlins apparently had doubts about Cronin reestablishing himself as an impactful pitcher in 2027. Even so, the timing of the release was callous. Rather than making him navigate the surgery and early rehab process on his own, they could have easily waited until the conventional 40-man roster cleanup period in November.
In free agency, Cronin signed a two-year minor league deal with the Texas Rangers. Many teams expressed interest in him, but the Rangers were the first to submit a written offer. “I’d play for Skip (Schumaker) any day, so I was really excited to see that he was over there,” Cronin said about reuniting with his 2024 manager. His former Fish teammates Jake Burger, Jonah Bride and Anthony Veneziano are also in the Rangers organization.